President Barack Obama has declared a national emergency in America as swine flu deaths reached 1,000. In Britain, meanwhile, 122 people have died and cases of swine flu have more than doubled in the past seven days.

The flu, which has spread throughout much of the world and raised global alarm, has caused the deaths of more than 100 children in the US alone, and is widespread in 46 of America's 50 states.

However, the White House said that declaring an emergency was a largely precautionary step aimed at allowing medical officials to bypass certain federal regulations in the event of a genuine disaster.

White House officials say the move was similar to precautions taken by coastal areas before a hurricane. "As a nation, we have prepared at all levels of government, and as individuals and communities, taking unprecedented steps to counter the emerging pandemic," Obama wrote in the declaration that he signed late on Friday night.

The emergency rules effectively cut through official red tape and free up resources to respond much faster in the event of a serious outbreak.

The rules will allow waivers in government health insurance programmes, and also make it much easier for hospitals to quickly treat and process any large and sudden influx of patients infected with swine flu, also known as H1N1 virus.

America is bracing for a particularly nasty flu season this year, accentuated by the rapid spread of swine flu. At the moment, cases of flu nationwide are at the same level of severity as at the peak of normal flu seasons, but this level has been reached far earlier than usual because of H1N1.

Most experts expect a surge of infections in the coming months, and during the spring of 2010.

Across the US, government officials have been offering free vaccines against swine flu, delivering millions of doses to concerned citizens. Health centres, clinics and hospitals have been flooded with people requesting the shots. Some areas have now run out of vaccines. Initially, the government thought 120 million doses could be available by mid-October, but the process has been hit by delays.

By the middle of last week only 11 million doses had been shipped to providers. But production, which relies on chicken eggs, is set to speed up rapidly. The government hopes to roll out around 50 million doses of swine flu vaccine by mid-November, and 150 million in December.

In Britain, the number of people who have died so far in the outbreak has increased to 122, with 93 deaths in England.

One in five deaths has occurred in children under 15 and 34% of deaths have been in people aged 16-44, according to data from the Department of Health.

Chief medical officer Sir Liam Donaldson said the pandemic will put unprecedented pressure on the health service for months to come as the second wave of the disease takes hold over the winter.

Cases almost doubled in the past week, with an estimated 53,000 new diagnoses of H1N1 in England in the past seven days. The number of people in critical care has reached its highest level yet at 99 out of 506 patients in hospital. One in four people in critical care is under 16.